Thermal insulation features for gas turbine engines

ABSTRACT

A hot section of a gas turbine engine includes a stator housing wall and an at least one insulating standoff attached to the stator housing wall, extending radially away from the stator housing wall. The hot section includes an accessory module attached to an opposite end of the at least one insulating standoff away from the stator housing wall.

BACKGROUND

The present disclosure relates generally to gas turbine engines. Morespecifically, this disclosure relates to insulation standoffs attachedto the casing of a gas turbine engine.

Aircraft with gas turbine engines can include, for example, Unpiloted(or Unmanned) Aerial Vehicles (UAVs) and expendable turbojet systems forguided munitions, missiles, and decoys. These aircraft are generallydesigned as limited lifetime vehicles, with expected lifetimes as shortas a single use or single mission vehicle. As such, many components andfeatures common in traditional piloted aircraft are unnecessary or canbe simplified for these aircraft applications, such as the thermalblankets commonly included on traditional aircraft engines.

One of the main components of many simple gas turbine engines is astator housing that encompasses a compressor, combustor, turbine, or acombination of these modules. As a result of the high gas temperaturesand pressures generated by these modules, the stator housing functionsas a pressure vessel and a thermal barrier to other componentsassociated with the gas turbine engine. For example, external componentsmounted on a gas turbine engine can include those that contain or conveyflammable fluids and the stator housing can operate above theauto-ignition temperatures of those flammable fluids. In the event of aleak or spill, the flammable fluids may combust, creating a safetycritical fire hazard.

SUMMARY

A hot section of a gas turbine engine includes a stator housing wall andan at least one insulating standoff attached to the stator housing wall,extending radially away from the stator housing wall. The hot sectionincludes an accessory module attached to an opposite end of the at leastone insulating standoff away from the stator housing wall.

A method of manufacturing a gas turbine engine with an insulatingstandoff includes manufacturing a stator housing wall and manufacturingan at least one insulating standoff configured to be attached to thestator housing wall, extending radially away from the stator housingwall.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a gas turbine engine.

FIG. 2 is a perspective view of a hot section of a gas turbine engine.

FIG. 3 is a perspective partial view of the hot section with insulationfeatures.

FIG. 4A is a perspective view of an insulation feature lattice network.

FIG. 4B is a perspective view of an insulation feature lattice networkwith ceramic infiltration.

FIG. 5 is a perspective view of one embodiment of a repeating sparassembly.

DETAILED DESCRIPTION

A gas turbine engine with integrally built insulation standoffssimplifies manufacturing. Even so, a gas turbine engine can leverageadditive manufacturing techniques to improve various aspects of the gasturbine engine such as, for example, limited-life engines. Additivemanufacturing allows the assembly details to be unitized, andsimultaneously permits integration of many complex performance-enhancingfeatures. The use of additive manufacturing to produce the enginereduces the time to delivery to the customer and lowers the overallproduction costs of the unit.

Disclosed herein is a gas turbine engine with integrally builtinsulation standoffs configured to maintain the temperature of theaccessory module below the auto-ignition temperature of any flammablefluids, generally accepted as 450° F. (232° C.). Many gas turbine enginesystems include thermal blankets, which are typically much less densethan metallic stator housings, but are applied at a thickness 5-10 timesthat of the metallic housing. On the whole, thermal blankets can add10-50% of the weight of the stator housing they are insulating. Buildingan integrally built insulation standoff obviates the need to providesuch a thermal blanket on the exterior of the stator housing,eliminating the need for cumbersome installation, reducing overallsystem weight, and simplifying ongoing maintenance.

FIG. 1 is a cross-sectional view of a gas turbine engine. FIG. 1 showsgas turbine engine 100 including compressor section 102, hot section104, exhaust section 106, combustor 108, rotor 110, stators 112, statorhousing wall 114, and axis of rotation X. In the illustrated embodiment,gas turbine engine 100, which may be an attritable or limited-lifeengine, shows compressor section 102 lying forward and adjacent to hotsection 104, which is positioned forward of exhaust section 106.Although combustor 108 lies physically aft of hot section 104, combustor108 fluidically sits between compressor section 102 and hot section 104.This arrangement may be referred to as a reverse flow combustor. Rotor110 extends along the axis of rotation X into both compressor section102 and hot section 104. Stators 112 are attached to stator housing wall114 and positioned in a compressed air flow path between compressorsection 102 and combustor 108.

Operationally, air enters the forward end of compressor section 102 andis compressed by compressor blades and vanes. Compressed air flowsaround stators 112 and is retained inside the compressed air flow pathby stator housing wall 114. Compressed air and fuel enter combustor 108where the compressed air and fuel are mixed and ignited. The resultinghigh-temperature gas from the combustor enters hot section 104 anddrives the rotation of turbine blades, which in turn generates power byturning rotor 110 circumferentially about axis of rotation X. Gas exitsgas turbine engine 100 out of the aft end of exhaust section 106.

Gas turbine engine 100 can be additively manufactured using techniquessuch as laser powder bed fusion, electron beam melting, direct energydeposition, and binder jetting. The additive manufacturing process canuse any suitable material, including without limitation metals, alloys,and ceramic based materials that can tolerate the high temperature andpressure environment of a gas turbine engine for the expected useablelife of the vehicle, such as, for example, nickel based alloys likeInconel® 625. However, guided munitions, missiles, and decoys aredesigned as single use vehicles and can have a maximum useable life of10 hours. Heat protection that extends the useable life of the vehiclebeyond 10 hours can unnecessarily add labor and expense to themanufacturing of such an engine. On the other hand, some UAVs can bedesigned to perform multiple missions and more heat protection may bedesirable. A specific metal or alloy with or without additionaltreatments to provide heat protection can be chosen with suchconsiderations in mind. For example, a thermal barrier layer or coatingcan be applied to the metal or alloy to extend the useful life of thegas turbine engine.

FIG. 2 is a perspective view of a hot section of a gas turbine engine.FIG. 2 shows gas turbine engine 100, hot section 104, exhaust section106, stator housing wall 114, insulation standoffs 116, and accessorymodule 118. Hot section 104 of gas turbine engine 100 is adjacent to andcircumferentially surrounds part of exhaust section 106. Hot section 104is also fluidically connected forward of exhaust section 106. Statorhousing wall 114 of hot section 104 encases combustor 108 and stators112 (shown in FIG. 1).

Insulation standoffs 116 can be integrally formed and conformal withstator housing wall 114. As used herein, the term “integrally formed”means manufactured as a single unitized part. As used herein, the term“conformal with” means to generally follow the shape of. For example,insulation standoffs 116 can be additively manufactured together withhot section 104 forming a single unitized manufactured part.Alternatively, insulation standoffs 116 can be manufactured separatelyfrom stator housing wall 114 and attached during the assembly processsuch as, for example, using welding or epoxy processes, riveting theparts together by adding an additional part or providing a rivet studand rivet aperture during manufacturing, or using a band clamp assembly,a cotter pin assembly, a push nut assembly, or any other suitablejoining method known in the art. Although insulation standoffs 116 aredepicted in FIGS. 2, 3, 4A, and 4B, as having a cylindrical shape,insulation standoffs 116 can have any shape that thermally insulatesaccessory module 118 from hot section 104 and simultaneously withstandsthe vibrational and thermal stress of gas turbine engine 100 during use.

Accessory module 118 can house or be an attachment site for variousparts associated with gas turbine engine 100 such as, for example, afuel tank, fuel pump, electronics, and pyrotechnics for kick startinggas turbine engine 100. Accessory module 118 can be integrally formedand conformal with insulation standoffs 116 at an end opposite to thesite of attachment between stator housing wall 114 and insulationstandoffs 116. Alternatively, accessory module 118 can be manufacturedseparately from insulation standoffs 116 and attached during theassembly process such as, for example, using welding or epoxy processes,riveting the parts together by adding an additional part or providing arivet stud and rivet aperture during manufacturing, or using a bandclamp assembly, a cotter pin assembly, a push nut assembly, or any othersuitable joining method known in the art.

FIG. 3 is a perspective partial view of hot section 104 with insulationstandoffs 116. FIG. 3 shows gas turbine engine 100, hot section 104,stator housing wall 114, insulation standoffs 116, and assembly module118. Stator housing wall 114 of hot section 104 encases combustor 108and stators 112 (shown in FIG. 1). Insulation standoffs 116 can beintegrally formed and conformal with stator housing wall 114 and extendradially away from stator housing wall 114. Alternatively, insulationstandoffs 116 can be manufactured separately from stator housing wall114 and attached during the assembly process.

Accessory module 118 can be integrally formed and conformal withinsulation standoffs 116 at an end opposite to the site of attachmentbetween stator housing wall 114 and insulation standoffs 116.Alternatively, accessory module 118 can be manufactured separately frominsulation standoffs 116 and attached during the assembly process.Although three insulation standoffs are depicted in FIG. 3, othernumbers of insulation standoffs can be used such as, for example, one,two, four, six, seven, ten, fifteen, twenty, or any number in between.Stator housing wall 114, insulation standoffs 116, and accessory module118 can all be formed of the same material or each can be formed of adifferent material. However, using three or more insulation standoffscompared to using one or two insulation standoffs reduces the amount ofvibrational stress experienced by stator housing wall 114, insulationstandoffs 116, and accessory module 118 during operation of gas turbineengine 100.

In some embodiments, insulation standoffs 116 have a diameter from 0.33inches to 0.50 inches, inclusive. In some embodiments, insulationstandoffs 116 extend radially away from stator housing wall 114 from0.25 inches to 2.00 inches, inclusive. Although insulation standoffs 116can also have other diameters and radial length extensions, thesegeometric parameters and other possible shapes are limited by factorssuch as, for example, vibrational effects experienced by stator housingwall 114, insulation standoffs 116, and accessory module 118 during useof gas turbine engine 100, the amount of heat transferred between statorhousing wall 114 and accessory module 118 during use of gas turbineengine 100, the weight of insulation standoffs 116, and the compactnessof the overall build of gas turbine engine 100.

FIG. 4A is a perspective view of an insulation feature lattice network.FIG. 4A shows gas turbine engine 100, hot section 104, stator housingwall 114, insulation standoff 116, and lattice network 116 a. FIG. 4Adepicts partially built insulation standoff 116 attached to statorhousing wall 114 of hot section 104. Partially built insulation standoff116 includes a repeating spar assembly (shown in FIG. 5) forming latticenetwork 116 a, which provides structural support to insulation standoff116 throughout the manufacturing process.

FIG. 4B is a perspective view of an insulation feature lattice networkwith ceramic infiltration. FIG. 4B shows gas turbine engine 100, hotsection 104, stator housing wall 114, and insulation standoff 116. FIG.4A depicts insulation standoff 116 attached to stator housing wall 114of hot section 104. Insulation standoff 116 includes lattice network 116a (shown in FIG. 4A) with ceramic infiltration. Insulation standoff 116can include walls to retain the ceramic infiltrate until the ceramicinfiltrate cures. Any ceramic infiltrate can be used such as, forexample, oxides and nitrides that can withstand the vibrational andthermal stress produced by gas turbine engine 100 under load. In oneembodiment, the ceramic infiltrate is a bentonite slurry.Advantageously, lattice network 116 a with a ceramic infiltratetransfers heat from stator housing wall 114 to accessory module 118 lessefficiently compared to a fully densified metallic structure having asimilar size and shape.

FIG. 5 is a perspective view of one embodiment of a repeating sparassembly. FIG. 5 shows spar assembly 138 including spars 132A, 132B,132C, 132D, 132E, and 132F, and center point 136. In the illustratedembodiment, there are six spars 132 radially extending from a centerpoint 136. Adjacent spars 132, for example spars 132A and 132B, lie atsubstantially 90° angles to one another. The ends of any three adjacentspars 132, for example spars 132A, 132B, and 132E, which are at anopposing end to center point 136, can form an abstract triangle. Takingall eight sets of three adjacent spars 132 and the resulting abstracttriangle from each set of three adjacent spars 132 forms an abstract3-dimensional shape, which can referred to as a square bipyramid.

Each spar 132 can have, for example, a diameter of 0.01 inches (0.25mm). In other embodiments, each spar 132 can have a diameter from 0.005inches (0.13 mm) to 0.02 inches (0.51 mm), inclusive. In otherembodiments, each spar 132 can have a diameter smaller than 0.005 inches(0.13 mm). In other embodiments, each spar 132 can have a diameterlarger than 0.02 inches (0.51 mm). Each spar 132 can have a length of0.05 inches (1.3 mm). In other embodiments, each spar 132 can have alength from 0.03 inches (0.76 mm) to 0.1 inches (2.5 mm), inclusive. Inother embodiments, each spar 132 can have a length smaller than 0.03inches (0.76 mm). In other embodiments, each spar 132 can have a lengthlarger than 0.1 inches (2.5 mm).

In other embodiments, spar assembly 138 includes more than six spars132. In other embodiments, spar assembly 138 includes fewer than sixspars 132. In other embodiments, two adjacent spars 132 can lie at anangle more than 90° from one another. In other embodiments, two adjacentspars 132 can lie at an angle from 45° to 90° from one another.

A gas turbine engine with integrally built insulation standoffsconfigured to maintain the temperature of the accessory module below theauto-ignition temperature of any flammable fluids, generally accepted as450° F. (232° C.) eliminates the need for a thermal blanket. Many gasturbine engine systems include thermal blankets, which are typicallymuch less dense than metallic stator housings, but are applied at athickness 5-10 times that of the metallic housing. On the whole, thermalblankets can add 10-50% of the weight of the stator housing they areinsulating. As such, the integrally built insulation standoff obviatesthe need to provide a thermal blanket on the exterior of the statorhousing, eliminating the need for cumbersome installation, reducingoverall system weight, and simplifying ongoing maintenance.

Discussion of Possible Embodiments

The following are non-exclusive descriptions of possible embodiments ofthe present invention.

A hot section of a gas turbine engine includes a stator housing wall andan at least one insulating standoff attached to the stator housing wallextending radially away from the stator housing wall. The hot sectionincludes an accessory module attached to an opposite end of the at leastone insulating standoff away from the stator housing wall.

The hot section of the preceding paragraph can optionally include,additionally and/or alternatively, any one or more of the followingfeatures, configurations and/or additional components:

The at least one insulating standoff is formed of a lattice network.

The lattice network is formed of a repeating network of spar assemblies.

Each spar assembly has a cubic shape.

Each spar has a diameter from 0.005 inches (0.13 mm) to 0.02 inches(0.51 mm), inclusive.

Each spar has a length from 0.03 inches (0.76 mm) to 0.1 inches (2.5mm), inclusive.

The lattice network of spars is infiltrated with a ceramic material.

The at least one insulating standoff is integral and conformal with thestator housing wall.

The at least one insulating standoff maintains an external temperatureof the accessory module at or below 450° F. (232° C.) during operationof the engine.

A method of manufacturing a gas turbine engine with an insulatingstandoff includes manufacturing a stator housing wall and manufacturingan at least one insulating standoff configured to be attached to thestator housing wall, extending radially away from the stator housingwall.

The method of the preceding paragraph can optionally include,additionally and/or alternatively, any one or more of the followingfeatures, configurations and/or additional components:

The at least one insulating standoff is manufactured integrally andconformally with the stator housing wall using an additive manufacturingprocess.

The method includes manufacturing an accessory module attached to anopposite end of the at least one insulating standoff away from thestator housing wall.

The at least one insulating standoff is a lattice network formed of arepeating network of spar assemblies.

Each spar assembly has a cubic shape.

Each spar has a diameter from 0.005 inches (0.13 mm) to 0.02 inches(0.51 mm), inclusive.

Each spar has a length from 0.03 inches (0.76 mm) to 0.1 inches (2.5mm), inclusive.

The method includes infiltrating the lattice network of spars with aceramic material.

The method includes configuring the insulation standoff to maintain anexternal temperature of the accessory module at or below 450° F. (232°C.) during operation of the engine.

A hot section of a gas turbine engine includes a stator housing wall andan at least one insulating standoff integrally and conformally attachedto the stator housing wall, extending radially away from the statorhousing wall. The at least one insulating standoff is formed of alattice network of spar assemblies and the lattice network of spars isinfiltrated with a ceramic material. The hot section includes anaccessory module attached to an opposite end of the at least oneinsulating standoff from the stator housing wall.

While the invention has been described with reference to an exemplaryembodiment(s), it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted forelements thereof without departing from the scope of the invention. Inaddition, many modifications may be made to adapt a particular situationor material to the teachings of the invention without departing from theessential scope thereof. Therefore, it is intended that the inventionnot be limited to the particular embodiment(s) disclosed, but that theinvention will include all embodiments falling within the scope of theappended claims.

The invention claimed is:
 1. A hot section of a gas turbine engine, thehot section comprising: a stator housing wall; an at least oneinsulating standoff attached to the stator housing wall and extendingradially away from the stator housing wall, wherein the at least oneinsulating standoff is formed of a lattice network of spars and thelattice network of spars is infiltrated with a ceramic material; and anaccessory module attached to an opposite end of the at least oneinsulating standoff away from the stator housing wall.
 2. The hotsection of claim 1, wherein the lattice network is formed of a repeatingnetwork of spar assemblies comprising spars.
 3. The hot section of claim2, wherein each spar assembly has a cubic shape.
 4. The hot section ofclaim 3, wherein each spar has a diameter from 0.005 inches (0.13 mm) to0.02 inches (0.51 mm), inclusive.
 5. The hot section of claim 3, whereineach spar has a length from 0.03 inches (0.76 mm) to 0.1 inches (2.5mm), inclusive.
 6. The hot section of claim 1, wherein the at least oneinsulating standoff is integral and conformal with the stator housingwall.
 7. The hot section of claim 1, wherein the at least one insulatingstandoff maintains an external temperature of the accessory module at orbelow 450° F. (232° C.) during operation of the engine.
 8. A method ofmanufacturing a gas turbine engine with an insulating standoff, themethod comprising: manufacturing a stator housing wall; manufacturing atleast one insulating standoff configured to be attached to the statorhousing wall such that the at least one insulating standoff extendsradially away from the stator housing wall; manufacturing an accessorymodule attached to an opposite end of the at least one insulatingstandoff away from the stator housing wall; and infiltrating a latticenetwork of spars with a ceramic material, wherein the at least oneinsulating standoff comprises the lattice network of spars.
 9. Themethod of claim 8, wherein the at least one insulating standoff ismanufactured integrally and conformally with the stator housing wallusing an additive manufacturing process.
 10. The method of claim 8,wherein the lattice network of spars is formed of a repeating network ofspar assemblies.
 11. The method of claim 10, wherein each spar assemblyhas a cubic shape.
 12. The method of claim 11, wherein each spar has adiameter from 0.005 inches (0.13 mm) to 0.02 inches (0.51 mm),inclusive.
 13. The method of claim 11, wherein each spar has a lengthfrom 0.03 inches (0.76 mm) to 0.1 inches (2.5 mm), inclusive.
 14. Themethod of claim 8, further comprising configuring the insulatingstandoff to maintain an external temperature of the accessory module ator below 450° F. (232° C.) during operation of the engine.
 15. A hotsection of a gas turbine engine, the hot section comprising: a statorhousing wall; an at least one insulating standoff integrally andconformally attached to the stator housing wall, extending radially awayfrom the stator housing wall, wherein the at least one insulatingstandoff is formed of a lattice network of spar assemblies and whereinthe lattice network of spars is infiltrated with a ceramic material; andan accessory module attached to an opposite end of the at least oneinsulating standoff from the stator housing wall.